I seem to remember that Beretta barrels for the autoloaders are interchangeable from the AL 2 through the 390. But I want to confirm that with folks more familiar with Beretta automatics and it's too late to call Beretta today. Thanks, in advance. JPM
Skeet is correct, the 303 barrel can be made to fit the 390, but the front lug will have to be angled to fit the 390 forearm, and the part where the gas piston sits in on the barrel will have to have holes drilled into the end of it, and channeled out to allow the gasses to bleed off, like how the 390 was intended to work!
Thanks for the information. I was not clear in my intent. I want to put a 390 barrel on the AL 2. I understand that the reverse will not work - I can't use an AL 2 barrel on a 390. But I left ambiguity in my question. JPM
At minimum, you'd need to figure out a way to plug the 4 gas vents in the front of the 390 gas cylinder. Not much thickness there, so drilling and tapping plug screws is out. Welding them closed would probably be your only option.